Sony TVs (well, all the ones I've used) have a VERY obvious degauss circuit - but only if you hard-power them on (without using the remote's standby button) - that's what that "frying pan" bonk sound is when you turn them on.

Power cycling a TV or repeatedly degaussing a computer monitor (allegedly) knackers the CRT (at least according to the instructions for my old CTX monitor), so is not to be recommended.  Certainly not power cycling a normal telly anyway, as that puts strain on the CRT's heating elements.

A tape bulk eraser has to be just as good as this thingy though?